为什么RHEL 6上没有ASMLIB?
有些人简单解释为Oracle为了推广自家的Oracle Linux而特意为之，实际上这一评价是不公允的。
ASMLIB的特殊性是它有部分Linux Kernel内核级别的组件， 而Kernel的开放与否完全取决于Kernel内核的维护者，对于Red Hat Enterprise Linux而言是Redhat公司。 由于Redhat公司从RHEL 6这个版本开始决定从Kernel中移除ASMLIB，并且不再给与Oracle公司对于该部分内核代码的访问修改权利，这直接导致Oracle不可能build出FOR RHEL 6的ASMLIB版本，因此显然这是Redhat的问题，而非O记得问题。
注意ASMLIB仅仅是不支持原生态的RHEL 6的Kernel，这不代表在RHEL 6上不可能用ASMLIB。Metalink文档介绍了相关信息：
What is ASMLib?
ASMLib is free, optional software for the Automatic Storage Management (ASM) feature of Oracle Database that simplifies the management and discovery of ASM disks and makes I/O processing and kernel resource usage with ASM storage more efficient. ASMLib is not required to use the Automatic Storage Management (ASM) feature of Oracle Database on Linux and all features and functionality of ASM will work without ASMLib.
Software Update Policy for ASMLib running on Red Hat Enterprise Linux
Oracle provides ASMLib software and support for customers who receive Red Hat Enterprise Linux (RHEL) operating system support from Red Hat and have a valid Oracle database support contract. Only the latest release of ASMLib will be provided for new Linux kernels released with each new RHEL minor release (“Update”). For example, if Red Hat were to release kernel 2.6.18-194.0.1.el5, Oracle will only release the latest version of ASMLib, say 2.0.5, for that kernel. Oracle will not release any previous versions of ASMlib for that kernel.
Furthermore, ASMLib software is only provided for Linux kernels for which the corresponding packages (devel, src, binaries) are available to Oracle. For example, Oracle cannot provide ASMLib software for kernels provided under Red Hat’s Extended Update Model or “z-stream” support.
Red Hat Enterprise Linux 6 (RHEL6)
For RHEL6 or Oracle Linux 6, Oracle will only provide ASMLib software and updates when configured Unbreakable Enterprise Kernel (UEK). Oracle will not provide ASMLib packages for kernels distributed by Red Hat as part of RHEL 6 or the Red Hat compatible kernel in Oracle Linux 6. ASMLib updates will be delivered via Unbreakable Linux Network(ULN) which is available to customers with Oracle Linux support. ULN works with both Oracle Linux or Red Hat Linux installations, but ASMlib usage will require replacing any Red Hat kernel with UEK
对于RHEL6，只要使用Oracle自己的Unbreakable Enterprise Kernel(UEK)内核则仍可以使用ASMLIB软件及其更新，仅仅是不支持RHEL 6自带的Kernel以及Redhat兼容的Kernel。 可以使用Unbreakable Linux Network(ULN)更新ASMLIB，前提是用户购买了Oracle Linux Support服务。 不管是Oracle Linux还是Redhat Linux均可以使用ULN服务，但是ASMlib要求必须将任何Redhat Kernel替换为UEK。
相关阅读：
在Linux 6上使用UDEV解决RAC ASM存储设备名问题
利用UDEV服务解决RAC ASM存储设备名
Why ASMLIB and why not?
如何诊断ASMLIB故障
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